1. Field of the Invention
The present invention relates generally to a fluorescent lamp and more particularly, to a fluorescent lamp for lighting.
2. Description of the Prior Art
The existing high power tubular fluorescent lamps (FL), e.g., T12, T10, T8, T5 and T4 FL etc. are the hot cathode FL. It has been used for lighting beginning around 1940, and is widely used in the world now. It has the advantages of high efficiency, low cost and able to generate different color light. However, it has a short operating lifetime, and very short ON/OFF switching lifetime. It is also, difficult to control and change the color of light emitted by the hot cathode FL or to change its color temperature.
The cold cathode fluorescent lamp (“CCFL”) has long operating lifetime, very long ON/OFF switching lifetime and high efficiency. It is widely used for LCD backlight, and some claims that the lifetime of CCFLs can be up to 60,000 hours. Cold cathode fluorescent lamp, or CCFL has been used to provide backlight for LCD display for some time. There are basically two types of CCFL backlight: (1) Edge type CCFL backlight; (2) Front type CCFL backlight; The Edge type has been the mainstream design for smaller size LCD backlights, while the Front type has emerged to be the mainstream design for the larger size LCD TV Displays.
There are three kinds of Front type CCFL backlight. A first type uses a tubular, U shape or serpentine shape CCFL in a housing, such as shown in U.S. Pat. No. 6,793,370 and U.S. Patent Pub. 2006/0023470. A second type uses a flat container containing electrodes and discharge gas to provide a flat light source. A third type uses dividers between two plates to create a serpentine shaped passage with electrodes at the two ends of the passage between the two plates in a vacuum environment to create a flat lighting source, such as shown in U.S. Pat. No. 6,765,633. All these three types of devices are used as LCD backlight. There are no controller or suitable outside connector used in conjunction with these designs to enable them to be used as general lighting devices.
The Edge type CCFL backlight needs relatively big reflector housing to provide uniform output through the whole surface, which is very important for backlight, but not for general lighting. While the other types of CCFL backlight have flat shapes, but their efficacy is relatively low due to short air discharge passage or too much heat generated during discharging. The third Front type CCFL backlight depends on using low melting point glass as building material, which can easily result in costly vacuum leaks so that it is difficult to maintain high vacuum for high CCFL efficacy.